<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CSS三角强化</title>
</head>
<style>
    .box{
        width: 0;
        height: 0;
        /*把上边宽度调大*/
        border-top:100px solid transparent;
        border-right: 50px solid skyblue;
        /*左边和下边的边框宽度设置为0*/
        border-bottom:0 solid blue;
        border-left:0 solid green;
    }

    .price {
        width: 160px;
        height: 24px;
        line-height: 24px;
        border: 1px solid red;
        margin: 0 auto;
    }

    .first {
        position: relative;
        float: left;
        width: 90px;
        height: 100%;
        background-color: red;
        text-align: center;
        color: #ffffff;
        font-weight: 700;
        margin-right: 5px;
    }

    .first i {
        position: absolute;
        right: 0;
        top: 0;
        width: 0;
        height: 0;
        border-color: transparent #ffffff transparent transparent;
        border-style: solid;
        border-width: 24px 10px 0 0;
    }

    .second {
        font-size: 12px;
        color: gray;
        text-decoration: line-through;
    }
</style>
<body>
<div class="box"></div>
<div class="price">
    <span class="first">
        ￥1650
        <i></i>
    </span>
    <span class="second">￥5650</span>
</div>
</body>
</html>